Re: Translate memory addresses

[Mark Kettenis <mark dot kettenis at xs4all dot nl>]

> Date: Tue, 08 Mar 2011 08:47:53 -0800
> From: Michael Eager <eager@eagerm.com>
> 
> Tom Tromey wrote:
> >>>>>> "Michael" == Michael Eager <eager@eagerm.com> writes:
> > 
> > Michael> I'm working with a target which needs to translate
> > Michael> a virtual memory addresses to a physical address
> > Michael> before accessing the target's memory or the core file.
> > 
> > Michael> Core_ops is defined in corelow.c, and there doesn't appear
> > Michael> to be an obvious hook for the target code to modify it to
> > Michael> add the translation routine.
> > 
> > Michael> Any suggestions on the best way to add a hook or how to specify
> > Michael> a target routine to do address translations for core files?
> > 
> > I am not an expert in this area, but couldn't you make a new
> > arch_stratum target that does the translation?
> > 
> > With this approach maybe you don't even need a hook -- just do the
> > translation and call the target beneath.
> 
> Interesting idea.  I didn't think of adding a stratum for translation.
> 
> I took a clue from the way that sol-thread.c prevents corelow.c
> from calling add_target to install core_ops.  I added the following
> to corelow.c:
> 
>    CORE_ADDR (*target_translate_address) (struct target_ops *, CORE_ADDR addr);
> 
> and in init_core_ops():
> 
>    core_ops.to_translate_address = target_translate_address;
> 
> The target code contains a definition for target_translate_address
> which is initialized to point to the translation routine.  For other
> targets, this will be zero.
> 
> It's inelegant, what can I say, but functional.

Did you look at how the BSD kvm target does things?  It does a
physical to virtual address translation (by using the system-provided
libkvm), and seems to get away with this without having such a hook.